Electric incandescent lamp



' ELEc nI INc NbEscENT LAMP v ,Filed Dec; 12, 1938 I COAT/N6 0F REFRACTORY V l2, szmaolvaucrok 01v suPPonra Inventor- I Johannes A MVanLiem tQ Hi2 Attohhey Patented Feb; 20,

Johannes A. M. van Liempt', Eindhoven, Netherlands, assignor to General Electric Company, a

corporation of New York Application December 12, 1938, Sa a No. 245,281"

- In the Netherlands December '31, 1937 My invention relates to electric incandescent la'mpsgenerally, and more particularly to support members for the-metal filaments of incandescent Electric vacuum-type incandescent lamps in,

which the filament is carried by the lead-in wires and also by one or several supports consisting.

of small hooks or-eyelets, have the disadvantage that these eyelets conduct away a part of the energy supplied to the filamentv in the form of heat as a result of which the filament, partic-,

'ularly at the points of support, adjusts itself to a somewhat lower temperature,-a fact which naturally has a detrimentalinfiuence on the emlfl clency of the lamp.

An attempt has been made to overcome this disadvantage by making the eyelets of carbides,

or by providing a metal core with oxides. However, it has been found that these known congo structions present very many difficulties so that In thisthey have never been used in practice. connection it should be remembered that the manufacture of incandescent lamps is a mass production in which it is generally highly ,un-

as desirable to make'the manufacture of one .part

1 of a lamp so complicated that the entire manufacturing process sufiers therefrom. The use of eyelets of the type indicated above cannot be carried out in practice. An eyelet made of car- I bide, for instance, must be baked separately, and

the finished eyelets are too brittle to be placed in the intended glass part of the lamp by means of machines. Furthermore, wires which are covered with the materials that have been suggested here; 5 tofore have proved to be unsuitable because it is difllcult to coat the materials on the core and be- ,cause, in addition, they break when bent or formed into the shape of eyelets.-

In a vacuum-type electric incandescent lamp,

40 according to the invention, in which the filament,

of tungsten for example, is carried by one or more support members or eyelets as well as by the lead-in wires, these eyelets are made of a metal core and the layer or coating provided thereon 45 consists of a semi-conductor having a melting point of more than 2700" C. The metal core, for instance molybdenum wire, may be provided, in a reducing atmosphere, with the particular semiconductor which is deposited from the gaseous 50 phase. Due to the fact that the melting point of the particular semi-conductor is more than 2700 C. (and, therefore, above the temperature which is normally assumed'by the filament *located in the lamp), the covering layeris, under 5 the given circumstances, inert with respect to the material of the filament. Tests have shown that as a result of the lower heat losses due to the coating of the eyelets with a thin layer of refractory semi-conducting material, an improvement in .efiiciency of "approximately four per cent 5 is obtained inthe lamp, according to the invention, as compared with lamps of otherwise similar qualities in which the eyelets have not been coated with such a layer.

The nitrides of a metal, which nitrides havea 10 melting pointof more than 2700" C., are very I suitable for use as the semi-conductors,according to the invention. As examples, the following may be mentioned:

Titanium nitride 'Zirconium nitride 2930 Tantalum nitride' 2800 Furthermore, carbides of metals can also be used according to the invention, which carbides have a higher melting point than the correspending nitrides. Some examples ofthese carbides are: Meltingpoint, 'C. Titanium, carbide 3400 Zirconium carbide ;e ;;c 3400 Tantalum carbide 4000 The above-mentioned conductors have the ad: I vantage 'thatthey can readily be placed on aj80 metal core. For instance, a molybdenum wire may be provided witha layer of titanium nitride by leading this wire, in the heated state, through a current of well-dried and oxygen-free mixing gas in which there is mixed titanium chloride vapoor. In this manner it is possible to provide a molybdenum wire, running 01? a spool in the above-mentioned atmosphere, with a thin layer of titanium nitride, and to rewind it on another spool. The'wire prepared in that manner can be 40 worked without any difficulty and in the same way as the normal molybdenum wire in an eyelet-inserting machine; in other words, the sup porting wires or eyelets can be placed. in the intended glass .part of the lamp by machine, while the wire, particularly when the thickness of the layer isnot too great, can be bent'irito the shape of eyelets without causing the layer or coating to break off or loosen. The vacuum-type coiled filament lamps equipped with these eyelets (for instance with 7 such eyelets) have an efficiency which, forinstance for the 220 volt 15 watt size,

is approximately five per cent higher than that of the corresponding lamps-in which the eyelets consist of the same total thickness of metal wire Melting point, C. I

without a covering layer. Another advantage or these semi-conductors over other covering materials lies in the tact that these materials have a coefllcient or expansion which is of the same order of magnitude as that of the customary eyelet material (tungsten or molybdenum) so that the layer will not tend to break'ofl when subjected to temperature changes.

The invention is uum-type lamps with straight filament and also in vacuum-type lamps with coiled filaments. Because the filament in the latter type is much shorter than in the rormer type. cause the filament length between two hooks is in this case always shorter, the advantage is the greates in this case. In the vacuum-type lamps with coiled filaments, the advantage will be greater the thinner the coil is. a

For a further understanding or theinvention reference may be had to the drawing which is a perspective view of a standard incandescent lamp mount in which may be incorporated support wires or eyelets of the vention. g

Referring to the drawing, the coiled filament I0 is supported at its ends by the lead-in wires H-ll. The filament is further supported intermediate its ends by the ends of support wires or eyelets I! the opposite ends or which are advantageous both in vacor rather be type comprising my insealed in the upper end or the glass arbor It. The said supportsvor eyelets l2 consist of metal wires (molybdenum or tungsten. for example) coated, in accordance with my invention, with a refractory semi-conductor, such as the nitride or carbide of titanium, zirconium or tantalum.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric incandescent lamp comprising a metal filament supported by lead-in wires and one ormore eyelets, said eyelets consisting of a metal core wire having thereon a coating consisting o! a semi-conductor having a melting point in excess of 2700" C.

2. In an electric incandescent lamp comprisng a metal filament supported by lead-in wires and one or more eyelets, said eyelets consisting 01a metal core wire having thereon-a coating consisting of one of the metallic compounds selected from the group consisting of nitrides and carbides having av melting point above 2700" C.

3. In an electric incandescent lamp comprising a metal filament supported by lead-in wires and one or more eyelets, said eyelets consisting of a metal core wire having thereon a coating consisting of one of the metallic compounds selected from the group consisting of nitrides and carbides of titanium, zirconium-and tantalum.

JO S A. M. van LIEMIPT. 

